急flex表单验证有关问题—同时验证两个文本框中必须填写其中一个，用flex的StringValidator如何验证的

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
               xmlns:s="library://ns.adobe.com/flex/spark" 
               xmlns:mx="library://ns.adobe.com/flex/mx"
               minWidth="955" minHeight="600">
    <s:layout>
        <s:VerticalLayout paddingLeft="40" paddingTop="40"/>
    </s:layout>
    <fx:Script>
        <![CDATA[
            import mx.controls.Alert;
            import mx.events.ValidationResultEvent;
            
            protected function button1_clickHandler(event:MouseEvent):void
            {
                // TODO Auto-generated method stub
                if (stringValidator1.validate().type == ValidationResultEvent.VALID ||
                stringValidator2.validate().type == ValidationResultEvent.VALID)
                    Alert.show("两者必须填写一个的情况成功发生。", "演示");
            }
        ]]>
    </fx:Script>
    <fx:Declarations>
        <!-- Place non-visual elements (e.g., services, value objects) here -->
        <mx:StringValidator id="stringValidator1" source="{this.textInput1}" property="text" required="true"/>
        <mx:StringValidator id="stringValidator2" source="{this.textInput2}" property="text" required="true"/>
    </fx:Declarations>
    <s:TextInput id="textInput1" />
    <s:TextInput id="textInput2" />
    <s:Button label="演示" click="button1_clickHandler(event)"/>
</s:Application>